According to the Ginzei HaMelech, the verse repeats that Mordechai adopted Esther because Esther acted like a daughter, obeying him the way a child should without rebellion.
According to the Malbim, this verse is emphasizing that Mordechai’s raising Esther meant that he educated her, in the sense of Rav Shlomo Wolbe’s theory of planting and building. A parent or a teacher has the dual role of physically planting ideas, but also building with the child’s potential. Perhaps such an idea can be used to explain why Avichayil is mentioned in this verse. He literally planted Esther, and Mordechai built upon her potential.